I think people are being rather pessimistic about the availability of less-expensive but decent kits. It appears to me that the Hilltopper kit might work for you.

I added a Hilltopper kit to both my wife's and my hybrids. The price varies according to the battery capacity you select, but approximately $450 (IIRC) gets you the front hub motor mounted on a decent wheel, the controller, a push button on/off throttle, and the 10 mile battery. It's very basic, but in my experience it works well. It's a 250W motor (i.e. low powered) that is primarily there to provide an uphill assist (thus "Hilltopper"), rather than turning the bike into a no-pedaling-required e-motorcycle.

We've had our Hilltopper kits for about 10 months now and have been very satisfied with them - just rode to the grocery store and back (hilly route) this afternoon, in fact.

IMO you could easily craigslist a decent bike for $100-$200 and put the kit on to meet your requirements.

As an added bonus, I see that you live in Tacoma, and Clean Republic is in south Seattle near Safeco Field. We bought ours from Liontail Cycles in Seattle, and either place would be able to let you see the kits and test ride demo bikes.

Good luck.